I. Field of the Invention
The present invention relates to a method of formulating a setpoint for a transmission of a motor vehicle power train in a situation termed cornering. It also relates to a device implementing such a method of formulating a setpoint.
This method applies advantageously to automated transmission devices in particular impulse Control Boxes termed BCI, Automatic Control Boxes termed BVA and Robotized Wear Boxes termed BVR, but also continuous-ratio transmissions, such as CVT (“Continuous Variable Transmission”), IVT (“Infinitely Variable Transmission”) and hybrid transmissions.
II. Description of the Related Art
A motor vehicle automated transmission conventionally comprises a control block receiving one or more input parameters interpreting inter alia, the desire of the driver. Then, as a function of the value of these parameters, the control block delivers a control setpoint with a view to an application to the wheels of the motor vehicle.
An upgrade of such a control block has already been described in document FR-A-2827339, in the name of the Applicant. This document details a device for controlling the operating point of a power train. The control carried out by this device is a torque control to be applied to the wheels of the motor vehicle. As defined in document FR-A-2827339, the value of the torque to be applied to the wheels of the motor vehicle is calculated directly at the wheels of the motor vehicle.
The device of document FR-A-2827339 possesses a module for interpreting the desire of the driver called an IVC module.
The IVC module generates a torque setpoint to be applied to the wheels destined for a block for optimization of the operating point OPF. The latter transmits said torque with a view to a torque control to be applied to the wheels of the motor vehicle. The OPF block simultaneously generates an engine revs setpoint on the basis of said torque to be applied to the wheels of the motor vehicle. This torque setpoint to be applied to the wheels of the motor vehicle is determined as a function of the desire of the driver, of the characteristics of the motor vehicle and of its environment, so as to best adapt the behavior of the motor vehicle, according to the driving situations.
In the cornering phase, a driver, at the steering wheel of a motor vehicle equipped with a conventional automatic transmission, has to cope with awkward driving situations.
For example, on approaching a corner, the driver generally eases off the accelerator pedal. The automatic gearbox which was previously in a given gear, then shifts directly to the gear above on account of the conventional shifting laws of an automatic gearbox. It thus deprives the motor vehicle of engine brake. The shift to the gear above then causes an unpleasant sensation of boarding of the motor vehicle.
In a driving situation, when the driver approaches a corner in a high gear, (fourth gear for example), and slows down through this corner, he is in general in the same high gear coming out of the corner. He must therefore depress the accelerator pedal to the maximum to cause the motor vehicle to pick up again. This action is often experienced badly by the driver and the passengers of the motor vehicle.
Methods and associated devices which make it possible to perform adaptations so as to attempt to improve passenger comfort in the cornering phase are already known in the prior art.
Document U.S. Pat. No. 5,514,051 filed by Porsche, proposes a method consisting in adjusting driving parameters of the motor vehicle as a function of predefined adjustment suites. When the motor vehicle is in a particular state, a cornering state for example a computer then refers to these predetermined profiles to adjust the driving parameters.
The solution proposed by document U.S. Pat. No. 5,514,051 makes it necessary to define, during the construction of each motor vehicle, a series of reference driving profiles.
A correction procedure based on laws for shifting gear ratios in a cornering situation according to various predetermined parameters such as for example the speed of movement or the lateral acceleration of the motor vehicle are also known through the documents FR-2 779 793 filed by the Applicant and FR-2 827 026 filed by the Applicant and PSA. These shifting laws make it possible to retain a gear ratio or to downshift in a cornering situation. This solution, adapted to automatic transmissions with discrete ratios is not at all so in the case of automatic transmissions with continuous ratios.
Document FR-2 834 939 in the name of the Applicant proposes to effect an adaptation of the control setpoint of the power train for particular driving phases especially during the cornering phases. The adaptation of the setpoint is done at the engine revs level.